How can I keep two different font sizes on two different documents?

Question

I am using Xubuntu and I need to keep document A with font size 8 and B with with font size 12. If I save A with font size 8, this switches the font size to 8 for all the other documents, including B. Again, if I open B, turn the font to 12 and save the document this switches A too to 12, and so on. This is rather boring. Somebody could tell me how to fix this problem?

Thanks

Edit: I am using the plain text editor of Xubuntu.

Answer 1

Changing the font size in a plain text editor will only change how your file is shown, but not, which font size it actually has (this can't be changed in a plain text file, it contains only the text, no formattings). If you want to have an document with different font sizes you have to use an office suite, for example Libre Office (http://www.libreoffice.org/)

Answer 2

What program are you using, in particular? If it's gedit, or other plain text editors, you're changing the settings, and thus the changes should actually reflect to all instances of it at once.
Otherwise, this sounds like a program bug.